Potassium rerr-butoxide

If, however, the base itself is a crowded one, such as potassium rerr-butoxide, even primary alkyl halides undergo elimination rather than substitution ... 

Double dehydrohalogenation to form terminal alkynes may also be canied out by heating geminal and vicinal dihalides with potassium rerr-butoxide in dimethyl sulfoxide. 

Potassium rerr-butoxide reacts with halobenzenes on heating in dimethyl sulfoxide to give rerr-butyl phenyl ether. 

Treatment of 460 with triethylamine in DMSO gave 15% of 461. This compound was also obtained from spiro complex 462 formed from 460 by the action of potassium rerr-butoxide (Scheme 73) (74ZOR826, 78ZOR105). 

Benzodiazcpine 4-oxides are also produced from 2-(chloromethyl)-l,2-dihydroquin-azoline 3-oxides 11. Thus, the action of potassium /< )7-butoxide on compound 11a gives the fused aziridine 12a, which readily isomerizes to the 5H-], 4-benzodiazepine 4-oxidc 13a on heating. The homolog lib similarly affords the 5//-benzodiazepine oxide 13b on treatment with potassium rerr-butoxide via the aziridine 12b, which, however, could not be isolated. Under different conditions, i.e. with aqueous ethanolic sodium hydroxide, compound 11b is transformed into the tautomeric 3//-1,4-benzodiazepine 4-oxide 14.222... 

Compound A (C4H10) gives two different monochlorides on photochemical chlorination. Treatment of either of these monochlorides with potassium rerr-butoxide in dimethyl sulfoxide gives the same alkene B (C4H8) as the only product. What are the structures of compound A, the two monochlorides, and alkene B ... 

Difluorododecanes 29 with potassium rerr-butoxide in tetrahydrofuran eliminate hydrogen fluoride stereoselectivcly the meso and syn compounds give, respectively, (E)- and (Z)-6-fluorododec-6-ene (30).26... 

O-tert-Butyl trichloroacetimidate, prepared in 70% yield by reacting potassium rerr-butoxide with trichloroacetonitrile, reacts with carboxylic acids and alcohols in the presence of a catalytic amount of boron trifluoride etherate at room temperature in cyclohexane-dichloromethane [Scheme 6.35], 7 The method also converts alcohols to ferr-butyl ethers (see section 4.3.2). A very similar reaction that allows /erf-butylation under essentially neutral conditions on a large scale involves reaction of a carboxylic acid with 3-4 equivalents of JV,N -di-isopropyl-Orerf-butylisourea88 [Scheme 6,36].56S9 The reaction proceeds via a tertiary carbocation ion intermediate and since capture of the cation is inefficient, excess isourea is required. The presence of alcohols is tolerated but not thiols or unhindered amines. The reaction conditions are compatible with a range of acid sensitive groups such as AMrityl derivatives and cydopentylidene acetals.90... 

Methyltellurophene To a mixture consisting of 10 m/ of hexamethylphosphoric triamide, 10 m/ of tetrahydrofuran, 0.5 g (6 mmol) of /err.-butanol, and 1.1 g (10 mmol) of potassium rerr.-butoxide are added 9.7 g (50 mmol) of 3-methylene-2,3-dihydrotellurophene. The mixture is heated at 50° for 1 h, water is added, the mixture is extracted with diethyl ether, the extract is washed with water, dried with anhydrous magnesium sulfate, filtered, and the solvent is evaporated. The residue is distilled under vacuum yield 8.7 g (90%) b.p. 72714 torr. 

In one case, a cyclopropane with one C-S bond has been converted to a cyclopropyl sulfide with another C-S bond. When 2-methylene-1-phenylsulfinylcyclopropane was allowed to react with a suspension of potassium benzylsulfanate and potassium rerr-butoxide in tetrahydrofuran, l-benzylsulfanyl-2-methylenecyclopropane (2) was formed in 59% yield. °... 

An exceptional example of a bromocyclopropane without a geminal methyl group, that undergoes elimination to give a methylenecyclopropane, is l-bromo-2,3-dimethylcyclopropane (7). Similar to the chloro analog vide supra), this compound gives an 84% yield of 1 -methyl-2-methylenecyelopropane (8) upon reaction with potassium rerr-butoxide in dimethyl sulfoxide at 80-90... 

Specific alkylation or acylation at the nitrogen has been observed in the case of secondary pyrrolidine enaminones in the presence of potassium rerr-butoxide. The configuration of the double bond was changed from Z to in this reaction (equation 105). 

An oxidation-cyclization was observed to take place on an indole enamine by simple swirling the solution in air in the presence of K2C03 (Scheme 19). For X = O, air-oxidation mediated by dimethyl sulphoxide and potassium rerr-butoxide resulted in dehydrogenation with formation of the 2-pyridone derivative. 

To a mixture of (2-methyl-l-propenyl)triphenylbismuthonium tetrafluoroborate (175 mg, 0.30 mmol), styrene (6 mmol) and dichloromethane (3 ml) was added potassium rerr-butoxide (34 mg, 0.30 mmol) at —78°C. The resulting mixture was allowed to warm to room temperature and was passed through a short silica gel column to give a cyclopropane in 85% yield [96JCS(P1)1971],... 

Furthermore, Diels-Alder cycloaddition of 15 and 2,5-diphenylisobenzofuran 86 yielded 87 (Eq. 28) which has been found to exhibit inclusion behaviour The fugitive didehydrotribenzo[a, c, ejcyclooctene 88 also underwent Diels-Alder reaction with 86 to furnish 89 (Eq. 29) Dehydrobromination of the bromide 90 with excess potassium rerr-butoxide in the presence of 86 afforded the trapping product 91 (Eq. 30) 5 ). 

STRATEGY AND ANSWER Here you want the Hofmann rule to apply (you want the less substituted alkene to be formed). Therefore, use a bulky base such as potassium rerr-butoxide in tert-butyl alcohol. 

Write the structure(s) of the major product(s) obtained when 2-chloro-2,3-dimethylbutane (either enantiomer) reacts with (a) sodium ethoxide (EtONa) in ethanol (EtOH) at 80 °C or (in a separate reaction) with (b) potassium rerr-butoxide ( -BuOK) in Tr-butyl alcohol ( -BuOH) at 80 °C. If more than one product is formed, indicate which one would be expected to be the major product, (c) Provide a detailed mechanism for formation of the major product from each reaction, including a drawing of the transition state structures. 

Make a reaction flowchart (roadmap diagram), as in previous problems, to organize the information provided to solve this problem. An optically active compound A (assume that it is dextrorotatory) has the molecular formula CyHuBr. A reacts with hydrogen bromide, in the absence of peroxides, to yield isomeric products, B and C, with the molecular formula C7Hi2Br2. Compound B is optically active C is not. Treating B with 1 mol of potassium rerr-butoxide yields (+)-A. Treating C with 1 mol of potassium rerr-butoxide... 

The synthesis of thieno[3,2- >]thiophene [17, 18] is shown in Scheme 3.3. The commercially available 3-bromothiophene undergoes formylation via lithiation at the 2-position and the addition of Al-formy[piperidine. Subsequent treatment of 3 with ethyl 2-sulfanylacetate affords the ester 4, which is converted to thieno[3,2- >]thiophene by hydrolysis and decarboxylation steps. The product is thus obtained in a very satisfactory overall yield of 60%. A similar method can be used to prepare thieno[2,3- >]thiophene from thiophene-3-carboxaldehyde via the carboxylic acid [19], but an attractive alternative route was published in full by Otsubo et al. [20] following a brief communication from de Jong and Brandsma [21], In this strategy, trimethylsilyl-l,3-pentadiyne is treated with potassium rerr-butoxide, butyllithium and carbon disulfide and then with ferr-butanol in HMPA, to obtain thieno[2,3-fi]thiophene in 46 % yield. The reaction sequence can be used to obtain the product in multigram quantities and the diacetylene derivative can be easily prepared from (Z)-l-methoxybuten-3-yne in 65 % yield. 

The ketone shown in Exercise 22.53 reacts with potassium rerr-butoxide in tert-h xXy alcohol to give a constitutional isomer of the bicyclic ketone shown above, (a) Write its structure and (b) explain its origin. 

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